1. Field of the Invention
The present invention relates to a positive active material composition for a rechargeable lithium battery, and more particularly, to a positive active material composition for a rechargeable lithium battery having improved cycle-life and thermal-stability characteristics.
2. Description of the Related Art
Currently, commercially available rechargeable lithium batteries substantially generate 4V in that they have 3.7 V of average discharge potential. Such a battery is considered an essential element in the digital generation since it is an indispensable energy source for portable digital devices such as a mobile telephone, a notebook computer, a camcorder and so on, which are generally abbreviated as the 3C devices.
For the positive active material in the rechargeable lithium battery, expensive LiCoO2 is used in more than 95% of the currently available batteries in the world market. In order to decrease costs of production, a great deal of effort is being exerted to find an alternative thereof to this positive active material. Although a rechargeable lithium battery using LiCoO2 powder as a positive active material has relatively good cycle-life characteristics and good flat discharging profiles, there are still demands for improvements in electrochemical properties, such as prolonged cycle-life and high power density characteristics.
As one scheme to satisfy such a demand, U.S. Pat. No. 5,292,601 discloses LixMO2 (wherein M is an element selected from Co, Ni, or Mn; x is 0.5-1) as an alternative to using LiCoO2 as a positive active material. U.S. Pat. No. 5,705,291 discloses a method for fabricating a rechargeable lithiated intercalation cell including the operations of mixing a coating composition including boron oxide, boric acid, lithium hydroxide, aluminum oxide, lithium aluminate, lithium metaborate, silicon dioxide, lithium silicate, or mixtures thereof, with a lithiated intercalation compound particulate, and fusing the coating compound at a temperature in excess of about 400° C. so as to coat the particulate with the fused coating compound.
However, there is still a demand for provision of a positive active material having an improved cycle-life performance.